It is known that in an internal combustion engine of an automobile or the like, oil as a lubricant may be deteriorated to generate sludge, which may affect relevant parts of the engine in various ways. The sludge contains olefin contained in the oil, NOx and SOx contained in a blow-by gas, and water as main components. The main components react in the presence of heat or acid to change to a precursor such as a sludge precursor or a sludge binder. Thus, the sludge is generated. The sludge appears to be mud or a slime-like substance. The sludge may disadvantageously deposit in, for example, a passage in the internal combustion engine to close the passage.
In particular, water generated inside the internal combustion engine by condensation or the like reacts with NOx and SOx contained in the blow-by gas to generate an acid substance. The acid substance serves as a catalyst for generation of sludge. Mixture of the acid substance into the oil promotes the generation of sludge, accelerates the deterioration of the oil, and degrades the functions of the lubricant.
In connection with the generation of the acid substance, conventional means adds an additive called a metal cleaning agent to the lubricant to neutralize the acid substance generated in the oil to inhibit the generation of sludge. Alternatively, a weak cationic surfactant is added to the oil to enhance the function of the oil for dispersion of the oil in the sludge (see, for example, Japanese Patent Application Laid-Open No. H9-13066(1997)).
The conventional art neutralizes and removes the acid substance contained in the oil to inhibit the generation of sludge. In other words, the main objective of the conventional art is to reduce the amount of sludge dispersed or diffused in the oil to inhibit the deterioration of the oil.
On the other hand, the sludge may disadvantageously adhere to or deposit in an area inside the internal combustion engine into which the oil does not always spread. That is, in an area into which the oil always spreads, even if sludge is generated, the sludge is washed away by the oil and is thus unlikely to adhere or deposit. However, in the area into which the oil does not always spread, the effect of washing away the sludge is not expected to work. Consequently, the adhesion or deposition may disadvantageously occur.
In view of these problems, an object of the present invention is to provide a sludge adhesion inhibiting structure for an internal combustion engine which can prevent the generation or adhesion of sludge in the area into which the oil does not always spread.